{"title":"Magnetism in 2- and 6-line ferrihydrite nanoparticles","authors":"","doi":"10.1016/j.rinp.2024.107916","DOIUrl":null,"url":null,"abstract":"<div><p>Magnetic properties of 2- and 6-line ferrihydrite (2LFh and 6LFh, respectively) as well as 2-line ferrihydrite embedded in SiO<sub>2</sub> (2LFh/SiO<sub>2</sub>) in the temperature range 2–380 K are investigated using DC magnetization and AC magnetic susceptibility measurements. All the samples exhibit superparamagnetic (SPM) responses at temperatures above their respective blocking temperatures in the range T<sub>B</sub> = 36–50 K. Linear extrapolations of 1/χ’ vs. T at 80 Hz and high temperatures give effective magnetic moment per atom μ<sub>eff</sub> = 5.78 μ<sub>B</sub> for 2LFh, μ<sub>eff</sub> = 6.27 μ<sub>B</sub> for 2LLFh/SiO<sub>2</sub> and μ<sub>eff</sub> = 5.20 μ<sub>B</sub> for 6LFh using Curie-Weiss law. The Arrhenius plots give anisotropy constants K = 4.5 × 10<sup>5</sup> J/m<sup>3</sup> for 2LFh, K = 5.5 × 10<sup>5</sup> J/m<sup>3</sup> and K = 1.5 × 10<sup>5</sup> J/m<sup>3</sup> for 6LFh using the particles size of 40, 35 and 60 Å derived from TEM data on the same samples. The number of uncompensated moments at the surfaces which contribute to the overall magnetic moments of the particles were estimated from the Néel model for antiferromagnetic nanoparticles and yielded magnetic moment per particle μ<sub>p</sub> ∼ 283 μ<sub>B</sub>, 251μ<sub>B</sub> and 465 μ<sub>B</sub> for 2LFh, 2LFh/SiO<sub>2</sub> and 6LFh, respectively. At 10 K, well thin the magnetic regime, the spins are blocked in specific directions resulting in usually large M<sub>S</sub> which appears to increase with decreasing nanoparticle size. Demagnetization behaviors were used as fingerprint techniques to identify the magnetic ordering and the nature of the interactions within the samples, they confirm the existence of AFM core at temperature below T<sub>B</sub> superimposed to a ferrimagnetic-like shell (at the surface). IRM/TRM measurements, particularly the TRM characteristic peaks at specific fields ranging from H = 10–40 kOe confirmed the existence of a spin-glass state below T<sub>B</sub> in the samples.</p></div>","PeriodicalId":21042,"journal":{"name":"Results in Physics","volume":null,"pages":null},"PeriodicalIF":4.4000,"publicationDate":"2024-08-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S2211379724006016/pdfft?md5=8fa763c9c6f5dea404da0d079c19854f&pid=1-s2.0-S2211379724006016-main.pdf","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Results in Physics","FirstCategoryId":"101","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S2211379724006016","RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"MATERIALS SCIENCE, MULTIDISCIPLINARY","Score":null,"Total":0}
引用次数: 0
Abstract
Magnetic properties of 2- and 6-line ferrihydrite (2LFh and 6LFh, respectively) as well as 2-line ferrihydrite embedded in SiO2 (2LFh/SiO2) in the temperature range 2–380 K are investigated using DC magnetization and AC magnetic susceptibility measurements. All the samples exhibit superparamagnetic (SPM) responses at temperatures above their respective blocking temperatures in the range TB = 36–50 K. Linear extrapolations of 1/χ’ vs. T at 80 Hz and high temperatures give effective magnetic moment per atom μeff = 5.78 μB for 2LFh, μeff = 6.27 μB for 2LLFh/SiO2 and μeff = 5.20 μB for 6LFh using Curie-Weiss law. The Arrhenius plots give anisotropy constants K = 4.5 × 105 J/m3 for 2LFh, K = 5.5 × 105 J/m3 and K = 1.5 × 105 J/m3 for 6LFh using the particles size of 40, 35 and 60 Å derived from TEM data on the same samples. The number of uncompensated moments at the surfaces which contribute to the overall magnetic moments of the particles were estimated from the Néel model for antiferromagnetic nanoparticles and yielded magnetic moment per particle μp ∼ 283 μB, 251μB and 465 μB for 2LFh, 2LFh/SiO2 and 6LFh, respectively. At 10 K, well thin the magnetic regime, the spins are blocked in specific directions resulting in usually large MS which appears to increase with decreasing nanoparticle size. Demagnetization behaviors were used as fingerprint techniques to identify the magnetic ordering and the nature of the interactions within the samples, they confirm the existence of AFM core at temperature below TB superimposed to a ferrimagnetic-like shell (at the surface). IRM/TRM measurements, particularly the TRM characteristic peaks at specific fields ranging from H = 10–40 kOe confirmed the existence of a spin-glass state below TB in the samples.
Results in PhysicsMATERIALS SCIENCE, MULTIDISCIPLINARYPHYSIC-PHYSICS, MULTIDISCIPLINARY
CiteScore
8.70
自引率
9.40%
发文量
754
审稿时长
50 days
期刊介绍:
Results in Physics is an open access journal offering authors the opportunity to publish in all fundamental and interdisciplinary areas of physics, materials science, and applied physics. Papers of a theoretical, computational, and experimental nature are all welcome. Results in Physics accepts papers that are scientifically sound, technically correct and provide valuable new knowledge to the physics community. Topics such as three-dimensional flow and magnetohydrodynamics are not within the scope of Results in Physics.
Results in Physics welcomes three types of papers:
1. Full research papers
2. Microarticles: very short papers, no longer than two pages. They may consist of a single, but well-described piece of information, such as:
- Data and/or a plot plus a description
- Description of a new method or instrumentation
- Negative results
- Concept or design study
3. Letters to the Editor: Letters discussing a recent article published in Results in Physics are welcome. These are objective, constructive, or educational critiques of papers published in Results in Physics. Accepted letters will be sent to the author of the original paper for a response. Each letter and response is published together. Letters should be received within 8 weeks of the article''s publication. They should not exceed 750 words of text and 10 references.